Internal fuel manifolds are typically installed within the combustor chamber outer casing (or gas generator casing) cavity with fuel nozzles thereof leading into the combustor chamber. Although they are not in the combustor chamber itself, they can be exposed to relatively high temperatures, especially in the case of gas turbine engines having a high pressure ratio.
If the temperature of the internal wetted surface of the fuel manifold in contact with the liquid fuel exceeds a given threshold, the fuel in contact with the wetted surface can form varnish which, with time, can convert to coke and reduce the fuel flow area. Eventually, performance of the fuel nozzles and durability of the hot section can be affected.
Accordingly, there remains room for improvement in addressing temperature control of the fuel manifold fuel conduits.